Vanadium-titanium magnetite is a composite ore with iron, vanadium, titanium and multiple valuable elements coexisting, is a major source of vanadium and titanium products in China and is mainly distributed in Panxi and Chengde areas of China with abundant reserves. At present, a traditional process flow for processing of the vanadium-titanium magnetite is as follows; the vanadium-titanium magnetite is subjected to mineral processing and separation to obtain iron finished ores and titanium finished ores, and then iron, vanadium and titanium are extracted by processing the iron finished ores and the titanium finished ores respectively, thus giving rise to long subsequent processing flow, low resource utilization rate and high cost. The iron finished ores are processed by adopting a ‘blast furnace-converter’ flow to produce iron and vanadium residue, and titanium in the iron finished ores is, however, wasted basically; and the titanium finished ores are mainly used for producing titanium dioxide, titanium sponge and the like, and iron in the titanium finished ores is, however, discharged in a form of ferrous sulfate solid wastes. Thus, the comprehensive utilization rate of vanadium resources is only 47%, the recovery rate of titanium resources is less than 15%, and therefore, resources are wasted seriously; and multiple roasting at high temperature is required in the subsequent process of extracting vanadium from vanadium residue to produce high energy consumption, and the problems, such as serious pollution from three wastes, low vanadium conversion rate and low product quality are caused. At present, the resource utilization rate of vanadium-titanium magnetite is far lower than the goal, in which the comprehensive utilization rate of vanadium resources is over 50%, the recovery rate of titanium resources reaches over 20%, and major coexisting rare metals, such as chromium, cobalt and nickel can realize large-scale recycling in the vanadium-titanium magnetite, of ‘the Twelfth Five-year Plan of Comprehensive Utilization and Industrial Development of Vanadium-Titanium Resources’ of China. In recent years, with the economic development of China and ever-increasing demand on products of vanadium, titanium and the like, the improvement of the technical level of the comprehensive utilization of vanadium and titanium in iron finished ores and titanium finished ores resources has a very important meaning in the sustainable development of the economy of China.
The hydrometallurgy has the advantages of high comprehensive recovery degree of valuable metals, relatively easy realization of continuity and automation of the production process, and the like, wherein acid leaching is the most commonly used leaching method in the hydrometallurgy. HCL has the advantage of high reaction capacity and has the capability of leaching oxysalts that cannot be leached by some sulfuric acids, and there have been relevant studies made in terms of processing titanium-containing minerals with the HCL, therefore, the HCL can be used for selectively leaching impurities in titanium finished ores and titanium residue to prepare artificial rutile. However, there has been no patent or report of using the HCL to directly process vanadium-titanium magnetite finished ores, and a solution obtained after leaching of finished ores by using HCL is complicated in component, large in quantity of impurity ions and difficult to separate. As an effective means for metal enrichment as well as purification and separation, the solvent extraction technique has the advantages of high recovery rate, simple process equipment, continuous operation and the like and is highly regarded in the industry. At present, as for the studies of extracting vanadium from an acidic vanadium-containing leaching solution, vanadium extraction from a sulfuric acid system is studied much more, and it is relatively difficult to extract vanadium from an HCL system with high acidity and high iron content.
Most vanadium in an HCL leaching solution of vanadium-titanium magnetite finished ores exists in a form of vanadyl ions (VO2+) and is capable of being extracted by using an acidic cationic extracting agent P204 or P507. However, since P204 or P507 has relatively high extracting capacity to Fe(III), Fe (III) becomes an important impurity element in the vanadium extraction process, and therefore, the leaching solution must be preprocessed before being extracted. Since the P204 or P507 has the capability of extracting Fe(III) rather than Fe(II), Fe(II) in the leaching solution needs to be reduced into Fe(I) to ensure that Fe in an aqueous phase exists basically in a form of Fe(II) and fails to be extracted by P204 or P507, and thus a purifying purpose is achieved. At present, all the enterprises where vanadium is extracted from an acidic leaching solution employ a Fe powder or sodium sulfite reduction method which can consume a large amount of reducing agent to cause great waste, and especially when iron chippings are used as a reducing agent, the iron content in a stock solution will be greatly increased to bring inconvenience to the subsequent procedures and greatly influence the vanadium extraction rate. At present, there has been no report that Fe(III) is reduced into Fe(II) by carrying out pre-reduction processing on vanadium-titanium magnetite finished ores so as to reduce the Fe(III) content in the leaching solution.
Generally, titanium residue is produced by taking titanium finished ores as a raw material through a high-temperature electric furnace smelting process. Owing to electric furnace smelting, the produced titanium residue has a relatively stable phase, and since concentrated sulfuric acid having the mass fraction of 92% is usually adopted for acidifying the titanium residue and acid liquor is difficult to recycle, a large amount of waste acid is discharged. At present, there has been no patent or report of preparing titanium residue from vanadium-titanium magnetite finished ores or bulk finished ores (a mixture of iron finished ores and titanium finished ores) by using a hydrometallurgical process.